1. Field of the Invention
The present invention relates to a multi-core optical fiber and a method of manufacturing the same.
2. Description of the Related Art
Multi-core optical fibers each having a plurality of core portions can be used in optical transmission paths that are required to have optical communication cables with densely packed optical fibers, and in optical interconnection systems that are required to have densely arranged wiring in devices. Similar to conventional optical fibers, some of the multi-core optical fibers include core portions whose refractive indices are different from each other, and confine light in the core portions due to the difference between the refractive indices of the core portions and a refractive index of the cladding portion (see, for example, M. Koshiba, et al., “Heterogeneous multi-core fibers: proposal and design principle”, IEICE Electronics Express, vol. 6, no. 2, pp. 98-103 (2009); hereinafter referred to as “M. Koshiba, at al.”). In a cross section perpendicular to a longitudinal direction of the multi-core optical fiber, the core portions are arranged separated from each other by a predetermined interval, and cross-talk between any pair of core portions becomes small so that the core portions can be closely packed.
To achieve a large effective core area (Aeff) of a single-mode optical fiber, an optical fiber has been proposed that has a trench-assisted refractive index profile (see, for example, M. B. Astruc, at al., “Trench-Assisted Profiles for Large-Effective-Area Single-Mode Fibers”, ECOC 2008, MO.4.B.1 (2008)).
In accordance with further increases in the capacity of optical communications, there is demand for multi-core optical fibers that have core portions arranged more densely and that make it possible to suppress cross-talk between the core portions.
It is an object of the present invention to provide a multi-core optical fiber that has core portions arranged more densely and that makes it possible to suppress cross-talk between the core portions, and to provide a method of manufacturing the multi-core optical fiber.